Historically, states annex what they conquer, then sign treaties formalizing their flag later.
The modern exception has been Russia's recent conquests in Georgia and Ukraine. Even if the Jews who settled the Golan aren't counted, given the current situation in Syria it's possible that if Israel gave up the Golan then the Golan's Druze and other Syrians would quickly vote to secede from Syria and join with Israel. Then the Golan Heights will be just as legally part of Israel as the Crimea is part of Russia.
Of course, if such a vote happens then Druze on the Syrian side of the border might vote to do the same. That would be a real mess: the Israelis wouldn't want to deal with it, nor the Syrian gov't in Damascus. So I imagine that after this SC vote many people will want to bury the issue again, as it has been for decades.